This invention relates to a water purification system, and more particularly, to a system that produces water meeting the standards of the United States Pharmacopoeia (USP) for purified water (USP purified water) or water for injection (USP WFI).
The pharmaceutical industry requires considerable quantities of water of high purity such as USP purified water and USP water for injection. The standards for each are well known but in general, USP purified water must be obtained from water which meets Environmental Protection Agency xe2x80x9cdrinking waterxe2x80x9d standards or comparable standards of the European Union or Japan. It must not contain any added substances and must be obtained by a suitable process and meet certain requirements relating to electrical conductivity as the electrical conductivity of water increases with the increasing presence of ions of various sorts, indicating impurities.
USP water for injection must meet all of the requirements of USP purified water. Further, it must be obtained by distillation or reverse osmosis and meet the requirements of the Bacterial Endotoxin test and contain no more than 0.25 Endotoxin units per milliliter. It must be prepared by a suitable method and apparatus so as to minimize microbial growth.
Systems utilized heretofore to produce such water are relatively complex, have a high microbial load and a relatively low purified water recovery rate. Many are approved only for USP purified water production and not approved for the production of water for injection. Depending upon the system, organic and microbial bioburden may be present throughout until the water to be purified is subject to heating in a distilling step. This can result in a high organic load and bioburden on the distillation apparatus. Where it is desired to reduce the bioburden on the distilling apparatus one may use a reverse osmosis purification step prior to the distilling step. While this may produce some improvement, the reverse osmosis membrane is subject to biofouling.
The systems also typically employ cartridge filters, multimedia filters and/or carbon filters. Multimedia filters typically remove suspended matter down to only about 20-30 microns and carbon filters having a high bio-growth rate and require regular sanitization which increases system maintenance costs.
Consequently, there is a real need for a simplified water purification capable of providing purified water to USP purified water or USP water for injection standards, and specifically a system that is relatively simple in construction and operation and which avoids high organic load and bioburden when distilling and which minimizes the potential for high biogrowth rates at various points in the system.
It is the principal object of the invention to provide a new and improved apparatus for purifying water to USP standards for purified water and/or water for injection. It is also an object of the invention to provide a new and improved method for purifying water to such standards.
According to one embodiment of the invention, an apparatus includes a filter connected for receiving feed water meeting USP standards. The filter is a microfilter or an ultrafilter having a nominal pore size of about 0.1 microns or less to be capable of removing bacteria and organic matter from the feed water. A dechlorinator receives filtrate from the filter and removes chlorine therefrom. The dechlorinator provides feed water to a vapor compression or multiple effect still which in turn distills the filtrate to a purity meeting USP requirements for purified water or water for injection.
In a preferred embodiment, a heat exchanger is adapted to receive the feed water to be purified to preheat the same to a predetermined temperature prior to its application to the microfilter or ultrafilter.
One embodiment of the invention contemplates the provision of a filtrate reservoir connected to the filter for receiving filtrate therefrom and that the filter be a backwashable filter. A backwash line is connected to the reservoir to receive filtrate from the reservoir and direct the filtrate in reverse flow through the filter to backwash the filter when required.
In one embodiment of the invention, there is further included a reverse osmosis membrane unit interposed between the still and the dechlorinator.
An embodiment of the invention also contemplates the provision of a filtrate treating anti-scalant device upstream of the still for treating filtrate so as to eliminate or minimize scaling within the still.
In one embodiment, the anti-scalant device is a water softening device located upstream of the dechlorinator and downstream of the reservoir.
In another embodiment of the invention, the filtrate treating anti-scalant device is a chemical injector for injecting anti-scaling chemicals into the filtrate downstream of the dechlorinator.
Other objects and advantages of the invention will become apparent from the following specification taken in connection with the accompanying drawings.